Overload protective device



ec. 553s, 1933a G, o. wnLMs 1,938,363

OVERLOAD PROTECTIVE DEVICE Filed May 2l, 1950 y 2 Sheets-Sheet l 1 Mmmm-um X7 Dec. 5, 1933 Q. Wim/ss 1,938,363

OVERLOAD .FROTEKCTIVE DEVICE Filed. May 21, 1950 2 Sheets-Sheet 2 Patented Dec. 5, 1933 UNITED STATES PATENT OFFICE mesne assignments, to

Allen-Bradley Company,

Milwaukee, Wis., a corporation of WMonsin Application May 21, 1930. Serial No. 454,287

18 Claims.

This invention refers more particularly to overload protective devices of the thermally actuated type and has as an object to simplify and improve the general construction thereof.

'5 Another object of this invention is to provide a protective device of the character described which is an entirely self-contained compact unit capable of being conveniently mounted directly on a portion of an electrical apparatus it is del signed to protect, a conventional outlet box cover,

or any other desirable support.

Another object of this invention is to increase the sensitivity of a thermal overload protective device and to thus materially reduce the time required to trip the same.

A more specific object of this invention resides in the provision of a novel heater element for an overload protective device of the character described which, by its design, has increased ef- 0 fectiveness and considerably reduces its trip-1 ping time.

'With the above and other objects in view which will appear as the description proceeds, my invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined vby the appended claims, it being understood that such changes in the precise embodiment of the herein disclosed invention may be made as come within the scope of the claims.

1n the accompanyingv drawings, l have illustrated one complete example ci the physical em bodiment ci my invention constructed according to the best mode I have so far devised for the practical application of the principles thereof,

and in which:

Figure l is a top plan view oi' an overload protective device constructed in accordance with my invention and illustrating the same mounted 4 on a conventional outlet box cover;

Figure 2 is a transverse sectional view taken through Figure 1 on the plane of the line 'ii- 2;

Figure t is a bottom view of the device shown detached from the outlet box cover;

Figure 4 is a transverse sectional view similar to Figure 2 and taken on the plane of the line i--i of Figure 1;

Figurel 5 is a perspective view oi the movable 5@ contacter carrying plunger and the movable contaeter;

Figure 6 is a. `schematic view illustrating the electrical circuit of the devicefand its connection in a typical motor circuit; and

Figure 7 is a view illustrating the manner of mounting the device directly on a motor housing or other similar electrical apparatus.

Referring now more particularly to the accompanying drawings in which like numerals designate like parts throughout the several views, the numeral 7 represents a body .or casing member within which the instrumentalities of the overload protective device are compactly housed so that the structure forms an entirely self-contained unit. The casing 7 is preferably molded 95 from suitable insulating material and is substantially cylindrical, having an annular flange 8 extended from its outer wall which is adapted to rest on the peripheral edge of an opening 9 formed in the desired support. In Figure l, the support is the cover 10 ot an outlet box 13 to which thecasing is secured by bolts or screws 11 passed through apertures in ears 12 extended from the casing outer wall and into suitable apertures in the cover.

It is very often desirable to mount the unit directly on some part ofthe electric translating machine it protects, as for instance the housing of an electric motor or the like, but existing overload protective devices are not adapted to so such installations.

The present invention overcomes this objectionable feature of existing structures by its compact unitary construction. Mounting the unit, therefore, requires only the drilling of a hole in the desired support and in Figure 7 the relay is shown mounted directly on one of the end bells of a motor M, its annular flangev 8 resting on the peripheral edge of a suitable opening drilled in the motor end bell. This manner of mounting simpliesthe connection of the unit in the motor circuit, as the leads then need not be brought out ci the motor housing.

Referring again to Figure 1, conduits 14 and 15 are connected with the outlet box 13 to carry 95 conductors 16 and 17, respectively, to the unit to be electrically bridged thereby as long as the circuit with which they are connected is free from overload conditions.

The casing or body 7 has a transverse partition 100 wall 18 which divides the same into upper and lower chambers 19 and 20, respectively, and the upper chamber 19 is subdivided into separated compartments by division walls or partitions 21.

The central compartment 22 defined by the di- 305 vision walls 21, has a switch mechanism 23 mounted therein which consists of a pair of stationary contacts 24 and 25 and a movable" contactor 26 normally bridging the stationary contacts., The stationary contacts 24 and 25 pr'.A 11

ject outwardly from the transverse partition 18 and have their inner ends extended through openings therein and directed laterally to form terminal flanges 27 and 28 which are connected with terminal posts 29 and 30, respectively.

The terminal posts 29 and 30 are suitably anchored to the transverse partition 18, and the lateral extensions of the stationary contacts, in being connected therewith, are likewise secured to the partition 18 to rigidly mount the stationary contacts. It is noted that the terminal posts are located in individual compartments on opposite sides of the central compartment in which the switch mechanism is disposed so that the division walls 21 provide the necessary electrical clearance and form protecting arc barriers between these elements. The division walls x 21 also serve to increase the strength o! the body or casing structure.

The movable contactor 26 is stamped from a piece of bendable metal as best illustrated in Figure 5 and has oppositely extending arms 31 which engage the stationary contacts, and a central laterally directed member 32 by which the contactor is connected with a plunger 33 formed of insulating material, see Figure 5.

The plunger 33 thus carries the contactor and provides means whereby the protective device may be manually reset after an overload has tripped the same, and to this end the plunger is longitudinally slidably mounted in the compartment 22 with its end opposite the contactor extended through an opening 45 in the side wall of the casing to provide a linger engaging portion. A stud 34 passed through an elongated opening 35 in the `plunger and anchored to the transverse partition 18 cooperates with the opening 45 to guide the movement of the plunger and a head 36 on the stud secures the plunger against detachment, the head.36 being received in a recess 37 surrounding the elongated opening 35. As best illustrated in Figure 5, the plunger has a recess 38 in its inner end to receive an expansive spring 39 which is confined between the movable contactor 26 and the bottom of the recess to normally yieldably urge the contactor toward the stationary contacts and provide contact pressure. The movement of the contactor with respect to the plunger which results from the action of the spring is however, limited by the engagement of lugs 40 formed on the inner end of the contactor lateral extension 32, with abutments 41 forming one end of a recess 42 communicating with the recess 38. The depth of the recess 42 is substantially equal to the thickness of the contactor extension 32 so that when the plunger is secured in its operative position within the casing the transverse partition ,18 cooperates with the recess 42 to prevent detachment of the contactor from the plunger.

The plunger also has a cavity 43 formed in its'under side in communication with the elongated opening 35, to receive an expansive spring 44. The spring 44 is confined between the bottom of the cavity 43 and the stud 34, as best illustrated in Figure 4, to at all times yieldably urge the plunger to its inoperative position disengaging the movable contactor from the stationary contacts; and as the distance of travel I of the plunger is greater than the total travel the device is tripped and the nger engaging portion projects considerably through the opening 45. To reset the same it is only necessary to move the plunger inwardly to its circuit closing position, and to hold the plunger in said position, a. spring member 46 is secured to one side of the plunger to engage its outwardly directed free end 47 with the teeth of a ratchet 48.

The ratchet 48 is mounted on the upper end of a hollow stem 49 which extends above and beneath the transverse partition 18 and is normally iixed theretoA by solder 50, so that the ratchet is stationary and the plunger, by the engagement of its spring member 46 with the ratchet, is held in its circuit closing position.

The' stem 49 is rigidly secured in a bushing 5l of heat resisting refractory material which in turn is secured in an opening formed in the partition 18 in any suitable manner. In the present instance, the opening in the transverse partition has a threaded portion in which the bushing 51 is loosely threaded, the space between the opening in the partition and the bushing being lled by a suitable plastic material such as cement or enamel. At the top of the bushing 51 a cup shaped washer 52 is secured which receives the lower reduced end 53 of the ratchet and serves as a reservoir for the solder 50 to hold the same when it melts.

Coiled about the lower end of the tubular stem 49 which is preferably formed of metal which is a good conductor of heat such as copper or the like, is a heating coil 54. It is noted that unrestricted access may be had to the stern lower end so that the heating coil may be easily applied or removed, or may be readily replaced by a coil of different dimensions.

The upper end of the coil is connected with the terminal post 29, as at 55, to be thus electrically connected with the stationary contact 24, and its lower end is connected with a terminal post 56, as at 57. In this manner, the heating coil 54 is connected in series with the switch mechanism 23 as clearly illustrated in Figure 6. The actual connections are as follows:

The conductor 16 which enters the outlet box 13 through the conduit 14 is passed upwardly through an opening 58 and is connected with the terminal post 56 which is mounted in a small compartment separated from the compartment in which post 30 is located, by a division wall 21'. The conductor 17 which enters the outlet box 13 through the conduit l5 is passed upwardly through an opening 59 and has its end connected with the terminal post 30 which is electrically connected with the stationary contact 25.

The circuit thus extends from the conductor 16 through the heating coil 54 to the stationary contact 24, through the movable contactor 26 to the stationary contact 25, and from the stationary contact 25 to the conductor 17; and as illustrated in Figure 6, the conductor 16 may be connected with a source of electrical energy, not shown, and the conductor 17 may lead to one side of a motor M the other side of which being connected with the source of energy through a conductor 60 in which a switch S may be interposed.

Upon the occurrence of an overload condition in the circuit, the resulting current rise produces a temperature rise in the heater unit which through radiation into the tubular stem 49, melts the solder holding the ratchet 48 against turning and permits the spring 44 to -snap the plunger to inactive position opening the circuit across the contacts 24 and 25.

Heretofore, the time required to trip an overload protective device of the character described very often was of such duration that v proper protection was not afforded and consequently the apparatus to be protected was damaged before the circuit could be opened. This invention, therefore, contemplates a novel means for hastening the tripping and to this end the heating coil 54 has its lower portion extended beyond the end of the tubular stern 49 and has its successive convolutions reduced ln diameter to form substantially a conical closure 61 for the lower end of the stem.

The closed end 61 oi' the heating coil prevents dissipation of the heat imparted to the stem 49 from its lower end and directs or forces the flow of heat upwardly to the solder at its upper end. 'I'he temperature of the solder is thus more quickly raised to its melting point so that the tripping of the device is effected in considerably less time.

As best illustrated in Figure 1, the casing has a protrusion 62 extended inwardly to form an arc guard or barrier between the contacts 24 and 25, and the entire' upper chamber 19 is closed by a cover 63 which is held in position by a screw 64 threaded in the stud 34. A boss 65 on the cover 63 in axial alignment with the stem 49 projects downwardly toward the ratchet 48 and has its inner end spaced slightly therefrom to provide means for preventing accidental displacement oi the ratchet 48, from its mounting stem when the solder is in a molten state.

` From the foregoing description taken in connection with the accompanying drawings, it will be readily apparent to those skilled in the art to which an invention of the character described appertains, that I provide a novel overload protective device which is particularly adaptable to installations where it is desirable to open a circuit upon the occurrence of comparatively small overloads, and one in which the tripping time-ls reduced to a. minimum by the provision of a novel heater unit. It is also apparent that the device of this invention is exceptionally compact and extremely simple in design, and lends itself readily to being mounted directly on part of the appliance it protects. v

What I claim as my invention is: Y

1. In an overload protective device, includin a circuit closure and means for releasably holding the circuit closure in closed position, said means releasing the circuit closure for opening upon an increase in temperature ,thereat, a member for conducting heat to the holding means, and a heating element surrounding the heat conducting member and extending beyond the end of the heat conducting member remote from the holding means for directing the heat given on by the heating element toward the holding means.

2. In an overload protective device of the character described including a circuit closure and means for holding the circuit closure in closed position, said means becoming inoperative upon an increase in temperature thereat, a member for conducting heat to the holding means, and a heating element juxtapose, a portion o! said member remote from the holding means, said heating element beingshaped to direct the ilow of heat given off thereby along said member toward the holding means. f

3. In an overload -protective device, a circuit closure normally yieldably urged to one position,

means to releasably hold the circuit closure in its other position includingv a member movable under certain conditions, thermally responsive means for normally securing said member against movement, a heat conducting member having one end juxtapose the thermally responsive means and its` other end remote therefrom, vand a heating element directly adjacent 'said other end of the heat conducting member remote from the thermally responsive means whereby the heat produced in sa'id element is conducted to the thermally responsive means by the conducting member, said heating element extending beyond the conducting member end to which it is adjacent and being of such shape as to cause the heat induced in the conducting member to travel toward the thermally responsive means.

4. In an overload protective device, the combination with a circuit closure normally yieldably urged to one' position, of means for releasably holding the circuit closure in its other position including, a mounting stem, a member on said mounting stem, thermally responsive means normally securing said member to the mounting stem, and a heater coil surrounding the mounting stem whereby heat given oiI by the heating element is is conducted to the thermally responsive means by the mounting stem, said heater coil extending beyond the end of the stem remote from the member thereon and the thermal responsive means whereby the heat flowing in the mounting stem is forced toward the thermally responsive means.

5. In an overloadprotective device, the combination with a circuit closure normally yieldably urged to one position, of means for releasably holding the circuit closure in its other position including, a mounting member, a stop member 'on said mounting member, thermally responsive means normally rigidly connecting said members adjacent one end of the mounting member, and aheating element juxtapose the other end of the mounting member whereby heat given off by the heating element is conducted to the thermally responsive means by the mounting member, said heating element extending beyond said other end of the mounting member for causing the flow of heat in the mounting member to travel toward the thermally responsive means.

6. In an overload protective device, the combination with a circuitclosure normally yieldably urged to one position, of means for releasably holding the circuit closure in its other position including, a stem, a stop member, thermally responsive means normally securing the stop member onV the stem, a heating element surrounding the stem whereby `the stem conducts heat to the thermally responsive means, and said heating element extending beyond the stem whereby the flow of heat in the stem is'forced toward the thermall responsive means,

7. In an overload protective device, the combination with a circuit closure normally yieldably urged to one position, of means for releasably holding the circuit closure in its other position including, a mounting member, a stop member, thermally responsive means normally securing the stop member to one end portion of the mount'- ing member, a heating element surrounding the other end portion of the mounting member and extending therebeyond whereby the heat transmitted to themounting member by the heating element is quickly conducted to the thermally responsive means by the mounting member.

8. In an overload protective device, the combination with a circuit closure normally yieldably urged to one position, of means for releasably holding the circuitl closure in its other position including, a' mounting member, a stop member, thermally responsive means normally securing the stop member to one end portion of the mounting member, a heating element surrounding the other end of the mounting member, said heating element having a portion extending beyond the mounting member and forming substantially a hood for the mounting member end whereby the heat imparted to the mounting member by the heating element is forced to flow along the mounting member toward the thermally responsive means.

9. In an overload protective device, the combination with a. circuit closure normally yieldably urged to one position, of means for releasably holding the circuit closure in its other position including, a mounting stem, a stop member, thermally responsive means normally securing the stop member to one end portion of the mounting stem, a coiled heating element surrounding the other end portion of the mounting stem, said heating element having a portion extending beyond the mounting stem end and having its coils which extend beyond the mounting stem of reduced diameter whereby the heat imparted to the mounting stem by the heating element is driven toward the thermally responsive means.

10. In an overload protective device, the combination with a circuit closurenormally yieldably urged to one position, of means for releasably holding the circuit closure in its other position including, a mounting stem, a stop member, thermally responsive means normally securing the stop member to one end portion of the mounting stem, a heating element coiled about the opposite end portion of the mounting stem, said heating element having certain of its convolutions extending beyond the mounting stem end and of reduced diameter to form substantially an enclosure for said opposite end portion of the mounting stem whereby the heat imparted to the mounting stem is driven toward the thermally responsive means.

11. An overload protective device comprising a body member having a dividing wall, a circuit closure disposed on one side of said dividing Wall, means normally yieldably urging the circuit closure to open position, releasable means for holding the circuit closure in closed position, thermal means on the other side of said dividing wall,

means extending through the dividing wall for thermal means for controlling said circuit mak` ing and breaking means and adapted to-upon an overload in a circuit with which the device is connected-effect opening of said circuit making Aand breaking means, and terminals one in each of other of said compartments for cond necting the overload protective device in the circuit, said division walls providing insulating barriers between the circuit making and breaking means and the terminals.

13. An overload protective device comprising, a ybase adapted to be mounted over a hole in the housing of an electric translating device to be protected by the protective device, so that the base forms substantially a continuation of the housing, a circuit closure carried by and above the base, thermally responsive means for releasably holding the circuit closure in one position also above the base, a heating element beneath the base to project into the housing of the electric translating device, and means for conducting heat from the heating element through the base to the thermally responsive means.

14. A protective overload device for an energy translating device, comprising an enclosure, a circuit closure within the enclosure, thermally responsive means within the enclosure for releasably holding the circuit closure in one position, a heating element without the enclosure, means for conducting heat from the heating element through one wall of the enclosure into the enclosure to the thermally responsive means, and means for attaching the enclosure to an outer wall of the energy translating device with said wall of the protective device enclosure closing an opening in said outer wall, and the heating element inside the translating device housing.

15. An overload protective device comprising an enclosure adapted to be mounted over a hole in the housing of an electric translating device to be protected by the protective device, a circuit closure within the enclosure, means for opening the circuit closure including a thermal element on the outside of one wall of the closure, and means for attaching the protective device to the translating device housing with said wall of its enclosure closing the opening and the thermal means within the housing to be inuenced by thermal conditions therein.

16. An overload protective device comprising a base, a circuit closure,- thermally responsive means for releasably holding the circuit closure in one position, said means becoming inoperative upon an increase in temperature thereat, said circuit closure and thermally responsive means being mounted above the base, a stem connected 

